The present invention relates firstly to a device for locking the connection of a heddle to a harness cord. Secondly, the present invention relates to a method for locking the connection of a heddle to a harness cord and to a Jacquard weaving machine provided with a device of this type for connecting a heddle to a harness cord.
In a Jacquard weaving machine, warp yarns are passed through the eye of a heddle, the Jacquard loom moving the heddles up and down by coupling or not coupling hooks to blades moving up and down in opposite phase, these hooks being connected to tackle cords in a tackle system. The tackle system is in turn connected to harness cords which are connected to the heddles. To lock the coupling between hook and blade during the movement of the hook with a blade, the heddles are connected at the bottom to return springs.
As has already been mentioned, on their top side the heddles are each connected to a harness cord. This connection is made by providing a securing element, which is an eye, a resilient fold-back, a clamping element, etc., at the end of the heddle, allowing the harness cord to be clamped in the securing element of the heddle or the harness cord to be wound around the securing element of the heddle and the folded-back harness cord to be connected to the incomer so as to form an eye in the harness cord.
These connections are made during the levelling of the eyes of the heddles through which the warp yarns extend. During levelling, the connection between the heddle and the harness cord is positioned in such a way that the heddle eye through which the warp yarn extends is in a position at a defined height with respect to the weft introduction means, in order to allow successful shed formation over the entire woven fabric. For this purpose, usually all the heddle eyes are positioned into the same defined height position.
In order firstly to ensure that these connections do not become loose and secondly to prevent the projecting parts of the connection from colliding with the heddles and cords located next to one another during the movement up and down, the prior art has disclosed various designs and methods for connecting the heddle to the harness cord and for locking this connection.
First of all, French patent publication FR 2212891 describes how a sleeve is arranged around the connection between heddle and harness cord, the sleeve being slid over one of the two components before they are connected. If, after the levelling of this heddle, the harness cord is connected to the heddle, the sleeve is moved over the connection and irradiated with a heat source. Since the sleeve is made from a material which shrinks under the influence of heat, the sleeve will stretch over the cord/heddle connection. The connection can only be broken by destroying the sleeve. When weaving in relatively high densities, the sleeve around one connection collides with adjacent connections between heddle and harness cord. Material which shrinks under the influence of heat is also less wear-resistant than certain other plastics materials which do not permit shrinkage through heat, with the result that collisions between the various sleeves quickly lead to wear, limiting the operating life time of the harness. The ends of the sleeves also have rather sharp corners, with the result that when the top side of one sleeve collides with the underside of the other sleeve, the sleeve is damaged, which leads to compression of material and accelerated wear to the connection. For this reason, the sleeves are designed to be slightly longer than the stroke of movement of the heddles, so that the said collisions cannot occur.
Long sleeves are expensive, cause problems during assembly and may be critical for determining the length of heddles or cords and may therefore have an adverse effect on the overall installed height of a Jacquard weaving machine. The connection can only be undone by destroying the sleeve.
European patent EP 0 932 713 describes an embodiment in which shorter shrink-fit sleeves can be used. Since the sleeves are pushed over an auxiliary piece at the bottom, the auxiliary piece being made from a more wear-resistant, non-shrinking plastic material and having a cross section which decreases in the downwards direction, there are no sharp comers on the ends. If adjacent heddles then move past one another and collisions occur between an auxiliary piece of this type and the top side of the sleeves around adjacent connections, the collision is prevented in this way from being front-on, which has a beneficial influence on the operating lifetime of the sleeves and the operating life time of the harness. However, the sleeves are still made from a material that is not very wear-resistant and are still subject to most wear at their free ends and at the location of the connection of the heddle to the harness cord, since there is a local projection there, and furthermore it remains the case that the connection can only be undone by destroying the sleeve.
Where in EP 0 932 713 the bottom piece is provided in sliding form by being made from wear-resistant plastics material, FIG. 6 of European patent publication EP 0 915 195 proposes a similar design on the heddle, the connection between the heddle and the wear-resistant plastic component, as the cross section decreases in the downwards direction, being fixedly connected to the heddle and also performing the function of the bottom wear-resistant plastic component, which is to reduce the effect of collisions. In this case too, a shrink-fit sleeve is used, first of all being arranged over the harness cord before being connected to the clamping part which is connected to the heddle and is slid downwards after this connection has been made. The same drawbacks apply here as were mentioned in the context of the discussion of EP 0 932 713.
French patent publication FR 2 822 479 describes a design for higher densities, in which, in addition to the wear-resistant plastic element at the bottom, an element is also provided at the top, having a cross section which decreases in the upwards direction, in order to avoid sharp corners. The said element includes a slot for clamping the harness cord after levelling, by sliding a sleeve, which connects the wear-resistant plastic element at the top and the bottom, over it in a clamping manner.
This embodiment requires three components to realize a clamping shield around the connection between heddle and harness cord, in which the sleeve may be shrunk-on or may be a tubular sleeve. On account of its limited wall thickness, the sleeve, over its entire length, is less stable and less wear-resistant than the injection-moulded elements at the top and bottom. The use of three components is also very laborious and time-consuming, making the operation particularly expensive.
US patent publication 2003/0188795 describes a solution comprising three parts, all the parts being made from a wear-resistant plastic and in their assembled form being responsible for retaining the connection between heddle and harness cord and for offering sufficient strength and operating life time for high densities of heddles and harness cords moving next to one another. One drawback which continues to be associated with this solution is that there are also three components, making the solution expensive and also making fitting to the connection laborious. Thus, the first part is placed on the heddle (without the securing element on the heddle being passed through the groove), after which the second part is then pushed over the end of the first part until it is clamped thereon, after which the first and second parts can be slid downwards over the heddle in order to make the connection to the harness cord onto which the third part has already been pushed. After this connection has been made, the third part is connected to the first and second parts which have already been connected.
A drawback of the designs and methods described above is that the mounting of the known devices on the connection between the heddle and a harness cord is very laborious and time-consuming.